Ion exchangers are used in many sectors such as, for example for softening water, for deionizing and purifying aqueous solutions, for separation and purification of sugar and amino acid solutions and for producing high-purity water in the electronics and pharmaceuticals industries. However, the conventional anion exchangers cannot be used under extreme temperature conditions. In particular, their thermal stability leaves something to be desired. If it is wished to avoid premature breakdown of the functional groups, the maximum temperature for a long term use must not be above 60° C. Even at room temperature, with conventional resins, a certain breakdown of the resin and release of the resin constituents into the surrounding solution, what is termed bleaching, is unavoidable.
For certain applications having high working temperatures in the range above 60° C., anion exchangers are required which withstand these elevated temperatures for a relatively long time period. Such conditions occur, for example, in deionizing in the heat-exchange of various machinery and plants, such as, for example, engines and power stations (conventional and nuclear). In such applications, the anion exchangers are usually used in combination with a cation exchanger, also in mixed form in what are termed mixed beds. In order to be able to comply with the task of deionizing, the anion exchangers must be used with OH− as counterion (what is termed the OH form).
EP-A 0 444 643 and JP-A 2003 230881 mention anion-exchange resins which can be used in the OH form at relatively high temperatures. The production pathway of these thermally stable resins proceeds via a complex chemistry which is associated with low yields. As a result, the availability of these resins is not assured in industrial amounts.